Oculocutaneous albinism type IV in Lhasa Apso, Pekingese, Pomeranian, and mixed breeds

Albinism is a congenital pigmentation disorder caused by reduced or completely absent melanin production. In the case of oculocutaneous albinism, this disorder affects both the eyes and the skin and coat. Affected dogs have very light to white or cream-colored coats, light blue eyes, and pink noses and lips. Reduced pigmentation is also evident in other structures, such as the eyelid margins, third eyelid, eyelashes, and inside the eye, particularly in the retinal pigment epithelium and choroid.

Albinism is typically associated with health complications such as photophobia (increased sensitivity to light), visual impairment, reduced protection against UV radiation, and the development of skin or ocular tumors.

The genetic basis of oculocutaneous albinism type IV in dogs is associated with the SLC45A2 gene. This gene contains the information necessary for the production of a protein important for the proper function of melanocytes. In Lhasa Apsos, Pekingese, Pomeranians, and mixed breeds, this condition is caused by the missense mutation c.1478G>A in the SLC45A2 gene.

The mutation is inherited in an autosomal recessive manner. This means that albinism develops only in individuals that inherit the mutated gene from both parents. Carriers of the mutated gene have normal pigmentation but can pass the mutation on to their offspring. When two heterozygous individuals are bred together, theoretically 25% of the offspring will be completely free of the mutation, 50% will be carriers, and 25% will inherit the mutated gene from both parents and display the albino phenotype.

Genetic testing can clearly determine the genotype of an animal and is a suitable tool for breeders to prevent the unintentional breeding of affected individuals.

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Reference:

Wijesena, H.R., Schmutz, S.M.: A missense mutation in SLC45A2 is associated with albinism in several small long-haired dog breeds. J Hered 106:285–288, 2015. PubMed reference: 25790827